Voltage runaway on the Pololu 5V, 9A Step-Down Voltage Regulator D24V90F5

Support Voltage regulators
1

I bought a Pololu 5V, 9A Step-Down Voltage Regulator D24V90F5 about half a year ago and put it into a vehicle to run two Raspberry PIs + Waveshare Displays. The board voltage is 12V.
For this, I soldered the wires directly into the board, added a passive heatsink and poured everything in electric resin to prevent issues with water/moisture.
I did not populate anything besides VIN/VOUT and GND.

Last year, everything worked as expected, the Raspberry PIs kept running even during motor start.

Now, after Winter, the output voltage drops way to low, reaching 4.60V when under 2-4A 5V load which is in no way near the rated limits (the heatsink does not even get warm).
This even happens when running of the battery or my lab power supply, so no motor is running.
This results in the Raspberry PIs crashing and not recovering.

Is this a technical defect? Is there anything I can do?
Thank you in advance!

2

Hello.

Given that we test every unit and it sounds like your board was working as expected for a while, this seems unlikely to be a defect, though it is possible that something has happened to damage the module. What is the output voltage if you test the regulator with a benchtop power supply with no load connected? Can you provide more details about your application (like what the typical power supply is) along with some pictures of your board and setup?

- Patrick